#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <pthread.h>

#define BUF_SIZE	1024
#define SMALL_BUF	100

void * request_handler(void * arg);
void send_data(FILE * fp, char * ct, char * file_name);
char * content_type(char * file);
void send_error(FILE * fp);
void error_handling(char * message);

int main(int argc, char * argv[]){
	int serv_sock,clnt_sock;
	struct sockaddr_in serv_adr,clnt_adr;
	int clnt_adr_size;
	char buf[BUF_SIZE];
	pthread_t t_id;
	
	if(argc != 2){
		printf("Usage : %s <port> \n",argv[0]);
		exit(1);
	}

	serv_sock = socket(PF_INET,SOCK_STREAM,0);

	memset(&serv_adr, 0, sizeof(serv_adr));

	serv_adr.sin_family = AF_INET;
	serv_adr.sin_addr.s_addr = htonl(INADDR_ANY);
	serv_adr.sin_port = htons(atoi(argv[1]));

	if(bind(serv_sock,(struct sockaddr *)&serv_adr,sizeof(serv_adr)) == -1){
		error_handling("bind error");
	}

	if(listen(serv_sock,20) == -1){
		error_handling("listen error");
	}

	while(1){
		clnt_adr_size = sizeof(clnt_adr);
		clnt_sock = accept(serv_sock,(struct sockaddr *)&clnt_adr,&clnt_adr_size);

		printf("connection request : %s %d\n",inet_ntoa(clnt_adr.sin_addr),ntohs(clnt_adr.sin_port));

		pthread_create(&t_id,NULL,request_handler,&clnt_sock);

		pthread_detach(t_id);
	}

	close(serv_sock);

	return 0;
}


void * request_handler(void * arg){
	int clnt_sock = *((int *)arg);
	char req_line[SMALL_BUF];
	FILE * clnt_read;
	FILE * clnt_write;
	char method[10];
	char ct[15];
	char file_name[30];

	clnt_read = fdopen(clnt_sock,"r");
	clnt_write = fdopen(dup(clnt_sock),"w");
	fgets(req_line,SMALL_BUF,clnt_read);

	if(strstr(req_line,"HTTP/") == NULL){
		send_error(clnt_write);
		fclose(clnt_read);
		fclose(clnt_write);
		return NULL;
	}

	strcpy(method,strtok(req_line," /"));
	strcpy(file_name,strtok(NULL," /"));
	strcpy(ct,content_type(file_name));
	if(strcmp(method,"GET") != 0){
		send_error(clnt_write);
		fclose(clnt_read);
		fclose(clnt_write);
		return NULL;
	}

	fclose(clnt_read);

	send_data(clnt_write,ct,file_name);	
}

void send_data(FILE *fp,char *ct,char *file_name){
	char protocol[] = "HTTP/1.0 200 OK\r\n";
	char server[] = "Server:Linux Web Server \r\n";
	char cnt_len[] = "Content-length:2048\r\n";
	char cnt_type[SMALL_BUF];
	char buf[BUF_SIZE];
	FILE * send_file;

	sprintf(cnt_type,"Content-type:%s\r\n\r\n",ct);
	send_file = fopen(file_name,"r");
	if(send_file == NULL){
		send_error(fp);
		return;
	}

	//send head
	fputs(protocol,fp);
	fputs(server,fp);
	fputs(cnt_len,fp);
	fputs(cnt_type,fp);

	while(fgets(buf,BUF_SIZE,send_file) != NULL){
		fputs(buf,fp);
		fflush(fp);
	}

	fflush(fp);
	fclose(fp);	
}

char * content_type(char *file){
	char extension[SMALL_BUF];
	char file_name[SMALL_BUF];
	
	strcpy(file_name,file);
	strtok(file_name,".");
	strcpy(extension,strtok(NULL,"."));

	if(!strcmp(extension,"html") || !strcmp(extension,"htm")){
		return "text/html";
	}else{
		return "text/plain";
	}
}

void send_error(FILE * fp){
	char protocol[] = "HTTP/1.0 400 Bad Request\r\n";
	char server[] = "Server:Linux Web Server \r\n";
	char cnt_len[] = "Content-length:2048\r\n";
	char cnt_type[] = "Content-type:text/html\r\n\r\n";
	char content[] = "<html><head><title>NETWORK</title></head>"
					"<body><font size=+5><br>br error filename request!"
					"</font><body><html>";

	fputs(protocol,fp);
	fputs(server,fp);
	fputs(cnt_len,fp);
	fputs(cnt_type,fp);

	fflush(fp);
}

void error_handling(char * message){
	fputs(message,stderr);
	fputs("\n",stderr);
	exit(1);
}